The recent rapid progress in standardization of a new high-density optical disc, for example, a BD-RE (Blu-ray Disc-Rewritable), capable of recording high-quality video data and high-quality audio data for a lengthy period of time has led to anticipation that the associated products will be developed and commercially available.
The BD-RE has, as shown in FIG. 1, a clamping area, transition area, burst cutting area (BCA) and lead-in area defined sequentially at the inner periphery thereof, and a data area and lead-out area defined respectively at the intermediate portion and outer periphery thereof.
The lead-in area is partitioned into a first protection zone Protection zone 1, a PIC (Permanent Information & Control data) zone, a second protection zone Protection zone 2, an information 2 zone Info 2, an optimum power control (OPC) zone, etc. Whereas the first protection zone and PIC zone are pre-recorded areas where data is pre-recorded in advance, the remaining zones of the lead-in area, the data area and the lead-out area are rewritable areas where new data is rewritten.
High frequency modulated (HFM) grooves are formed in the PIC zone, in which main information of the disc to be permanently preserved is stored. These HFM grooves are modulated by a bi-phase modulation method to store disc information (DI), as shown in FIG. 2.
That is, HFM grooves are modulated in the radial direction with a rather high bandwidth signal, to create a data channel for replicated information with sufficient capacity and data rate.
In this modulation method, a bit with value 0 is represented by a transition at the start of the bit cell and a bit with value 1 is represented by a transition at the start and in the middle of the bit cell. The modulated bits are recorded on the disc by a deviation of the groove from its average centerline as indicated in FIG. 2. The length of each bit cell shall be 36T, where T corresponds to the length of a channel bit in the rewritable data areas.
The disc information (DI) contains, as shown in FIG. 3, channel bit length information with a size of 1 byte, which is detected based on a push-pull signal. Four bits b7 to b4 of the channel bit length information are reserved bits having values of ‘0000’, and the remaining four bits b3 to b0 represent the channel bit length of main data such as an A/V stream.
For example, the remaining four bits b3 to b0 represent that the channel bit length of the main data is 80 nm and the recording capacity of the optical disc is 23 Gbytes if they are ‘0000’, that the channel bit length is 74.5 nm and the recording capacity is 25 Gbytes if they are ‘0001’,and that the channel bit length is 69 nm and the recording capacity is 27 Gbytes if they are ‘0010’.
In this connection, an optical disc device selects a partial response maximum likelihood (PRML) corresponding to the recording capacity of the BD-RE with reference to the channel bit length information contained in the Disc Information and performs a bit detection mode appropriate to the selected PRML, so as to normally perform a data playback operation.
Meanwhile, the standardization of a new high-density optical disc, as well as the BD-RE, is recently under discussion among the associated companies. The new high-density optical disc may be, for example, a BD-ROM, which has, as shown in FIG. 4, an inner area, clamping area, transition area, information area and rim area.
The information area includes a BCA, and a PIC zone in which disc information (DI) is recorded. This DI is recorded in the PIC zone in a straight pit type that is the same recording format as that of main data recorded in a data zone.
The DI recorded in the straight pit type must be subjected to a decoding process since it is detected in a radio frequency (RF) signal detection mode, not in a push-pull signal detection mode. However, there is a problem in that an error occurs in the data playback operation if channel bit length information recorded in the DI is not normally detected in the early stage of the data recording/playback operation.
Also, because the DI only can be read after full start-up of the drive, it takes a time to start recording or playback of data.